SUBLETHAL EFFECTS OF REPEATED INTRAPERITONEAL CADMIUM INJECTIONS ON RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Acute and chronic effects of cadmium have been widely described for di fferent aquatic organisms and exposure routes, However, there is clear ly a lack of information on the potential of cadmium to cause genotoxi c effects. This work presents genotoxic and nongenotoxic parameters an alyzed in cadmium-exposed rainbow trout. The assessment was performed for sublethal levels after long-term exposure using six intraperitonea l injections of 0.5 mg/kg (Day 1), 1 mg/kg (Days 3, 7 and 11), and 2 m g/kg (Days 15 and 19) to allow precise estimation of the dose. Cadmium accumulation in target tissues, essential metal mobilization by cadmi um at the subcellular and tissue levels, and induction of metallothion eins were selected as exposure and effect parameters. Induction of mic ronuclei and variation in DNA content (expressed as variation coeffici ent in the G(1) phase of the cell cycle) in blood cells, determined by how cytometry, were selected as biomarkers for genotoxic effects. Cad mium accumulation, induction of metallothioneins, and mobilization of essential metals at the subcellular level were observed in different o rgans in response to cadmium exposure. The highest metallothionein ind uction was observed in liver, reaching 270 +/- 90 nmol/g wet tissue in treated fish versus 2.68 +/- 1.1 nmol/g wet tissue in controls. The h ighest cadmium accumulation was also observed in the liver (27.8 +/- 9 .5 pg Cd/g wet wt in treated animals versus 1.0 +/- 1.7 in the control group). However, no genotoxic effects were observed in blood cells. T he frequency of micronuclei was 0.012 +/- 0.008 for the control group and 0.013 +/- 0.021 for treated animals. The variation coefficient of G(1)-phase nuclei was 3.61 +/- 0.66 and 3.22 +/- 0.29 for control and cadmium-exposed groups, respectively. Thus, it is concluded that under the experimental conditions employed here, treatment of rainbow trout with cadmium chloride at doses that produce significant toxicological alterations at the tissue and subcellular levels does not provoke obs ervable alterations in the genotoxic parameters considered in this stu dy. (C) 1998 Academic Press